The present invention relates to switch mechanisms particularly adapted for use in passive restraint seatbelt systems in automobiles and other vehicles.
The number of seating positions for all sizes of automobiles can vary between four and six, each being provided with seatbelts, and for some positions, shoulder restraining belts and related equipment. Part of this equipment includes electrical switches in circuits which are utilized to warn occupants that their seatbelts are not connected and/or in use, or as an interlock device which is adapted to inhibit operation of an automobile unless all occupied seats have their respective seatbelts connected. Interlock systems may also be connected to automobile doors and to an alarm system for warning the driver or passengers.
The presence of seatbelts, the attendant electrical circuits and switches therefor, and interlock structure for each of the seating positions of an automobile has increased the cost of automobiles for the manufacturer and consequently, to the ultimate purchaser. As is well appreciated, the automobile industry is the most competitive market in the world today with the industry turning out millions of automobiles every year along with the many replacement parts therefor.
Because of their highly competitive activity, it is incumbent upon manufactureres to carefully analyze and review the design and cost of each of the thousands of parts and components which go into the finished automobile. Generally no item is overlooked in these investigations, and every chance is taken to achieve a competitive edge by simplifying, redesigning and utilizing cost effective procedures to bring down the unit manufacturing cost of the automobile.
In the case of seatbelt safety systems, one area of design which can be costly is in the provision and use of electrical switches. In the case of the need for four to six seatbelt mechanisms per car, there would be a corresponding need for four to six switching mechanisms for the safety alarm or for any other systems which may inhibit automobile operation if such were intended. A thorough costing investigation, therefore, would include a study of the switching mechanisms in order to achieve low cost items for this purpose. In achieving low cost, however, it must be remembered that such a goal must be accomplished without detracting whatsoever from the efficiency, the dependability, and the life span of the switching mechanism while still maintaining the safety precautions these items were designed to provide.
Another consideration the manufacturer must bear in mind during design study of seatbelt systems and safety switches is the need to consider the particular environment for switch mechanisms associated with seatbelt systems. The life span of the conventional car takes it through periods of extremes in weather: very hot and humid to very cold and dry. The life span will also include hundreds of hours of driving in heavy rain and snowstorms when switching mechanism become wet and exposed to moisture condensation. In addition, during the many miles of the life span of the car, the slow buildup of dust and contaminants is ever prevailing and damaging with such dust and contaminants working their way through the very fine spacing between switching parts and related structure to cause eventual failure of the switching mechanisms.